One of the most difficult problems to be solved when manufacturing an optical material by thermally curing a polymerizable composition which includes a polymerization reactive compound (also described below as a polymerization monomer or monomer) is striae. Striae are marks generated during the cast polymerization of monomers, or flowing marks which are cured by convection due to the influence of heat generation of monomers during polymerization, temperature difference with the surroundings, or the like. Specifically, striae are extremely likely to occur in thick items.
As a method of suppressing striae, curing may be carried out slowly over a long period of time such that the monomer does not flow, or underwater polymerization or the like may be performed to increase the heat conduction.
According to the apparatus for manufacturing a plastic lens described in Patent Document 1, it is possible to provide an apparatus for manufacturing plastic lenses which is compact and has excellent space efficiency and which is able to manufacture a plastic lens during one revolution of a mold injected with a plastic composition placed on a rotary table.
In addition, for example, there are a method in which a monomer composition is thickened to a specific range by a preliminary reaction, and then polymerized and cured by a heating polymerization program similar to a conventional manufacturing method (Patent Document 2), a method in which, in the middle of a step of polymerizing and curing a monomer composition, a molded article filled with the monomer composition is forcibly moved regularly or irregularly so as to eliminate unevenness of the monomer during curing and to suppress the generation of optical distortion or striae (Patent Document 3), a method of optimizing a temperature program when polymerizing a monomer composition (Patent Document 4), a method of holding and curing a molded article filled with a monomer composition at a specific angle from the horizontal plane when polymerizing and curing a monomer composition (Patent Document 5), a method of polymerizing by irradiation with microwaves in a state where a mold filled with a monomer composition is immersed in a liquid (Patent Document 6), and the like.
As a composition for an optical material which includes a polyether-modified compound, the techniques described in Patent Documents 7 to 9 are known.